The two suitors have been trying to one-up the other's bids for the company by raising their purchase price and sweetening the pot for Asarco's numerous creditors, who have billions of dollars in claims against the company.

The one-upping continued earlier this week with both Grupo and Sterlite increasing their offers for the company.

Sterlite increased the cash portion of its bid in light of rising copper prices to $1.59 billion from $1.1 billion while lowering the note portion of the offer to $208 million from $770 million.

Grupo said it increased the cash portion of its bid by about $260 million to about $1.72 billion. Combined with a $280 million in notes, the total amount of Grupo's bid is about $2 billion.

A third prospective buyer, New York City-based Harbinger Capital Partners, backed out of a $500 million offer last week. The hedge-funder manager, one of Asarco's largest bondholders, said it would back Sterlite's plan.

The hearings, which are intended to determine which of the two reorganization plans get confirmed, are slated to last several days in U.S. Bankruptcy Court in Corpus Christi.

Asarco, which operates three copper mines and a smelter in Arizona, filed for bankruptcy protection in 2005 amid a workers strike and billions of dollars of environmental- and asbestos-related claims.

Much is riding on the company's reorganization efforts, including a $1.1 billion settlement to resolve an estimated $6.8 billion in environmental claims over polluted mine sites that a bankruptcy judge approved in June.